The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Referring now to FIG. 1, a communication system 10 is shown as an example of a signal processing system. Other examples include radar systems, automated test equipment (ATE), and so on. The communication system 10 comprises an information source 12, a transmitter 13, a communication channel 20, a receiver 27, and a destination 28. The transmitter 13 comprises a source encoder 14, a channel encoder 16, and a modulator 18. The receiver 27 comprises a demodulator 22, a channel decoder 24, and a source decoder 26.
The information source 12 may be an analog source such as a sensor that outputs information as continuous waveforms or a digital source such as a computer that outputs information in a digital form. The source encoder 14 converts the output of the information source 12 into a sequence of binary digits (bits) called an information sequence u. The channel encoder 16 converts the information sequence u into a discrete encoded sequence v called a codeword. The modulator 18 transforms the codeword into a waveform that is suitable for transmission.
The waveform output by the modulator 18 is transmitted via the communication channel 20. Typical examples of the communication channel 20 are telephone lines, wireline communication channels, wireless communication channels, optical fiber cables, and so on. Noise such as electromagnetic interference, inter-channel crosstalk may corrupt the waveform.
The demodulator 22 receives the waveform. The demodulator 22 processes each waveform and generates a received sequence r that is either a discrete (quantized) or a continuous output. The channel decoder 24 converts the received sequence r into a binary sequence u′ called an estimated information sequence.
The source decoder 26 converts u′ into an estimate of the output of the information source 12 and delivers the estimate to the destination 28. The estimate may be a faithful reproduction of the output of the information source 12 when u′ resembles u despite decoding errors that may be caused by the noise.